References
- Butterflies 2000: On the Wings of Freedom. Butterflies for kids: "The story of Cathy the caterpillar." http://library.thinkquest.org/C002251/cgi-bin/default.cgi?language=english&mode=chapter&outputmode=0&navmenu=1&javascript=1&chapter=0§ion=3
- National Research Council. 1996. National science education standards. Washington, DC: National Academy Press.